The present invention relates to a new class of diimino compounds useful as ligands for obtaining late transition metal complexes covalently bonded to an inorganic support.
It has been recently discovered that alpha-diimino ligands can be used for synthesizing complexes of late transition metals that are useful as catalyst for polymerizing olefins. For instance WO 96/23010 discloses, with several examples, various types of nickel or palladium diiniine complexes, showing that they can be used for polymerizing a large number of olefins.
In WO 98/27124 and WO 98/30612 2,6-pyridinecarboxaldehydebis(imines) and 2,6-diacylpyridinebis(imines) complexes of iron and cobalt are disclosed for polymerizing ethylene and propylene. WO 99/12981 relates to substituted 2,6 diimino pyridines complexes of Fe[II], Fe[III], Co[I], Co[II], Co[III]), Mn[I], Mn[II], Mn[III], Mn[IV], Ru[II], Ru[III] and Ru[IV].
Immobilizing these complexes on solid supports to enable heterogeneous polymerization process such as those based on gas phase, bulky or slurry processes, is important for their efficient industrial utilization. In particular, some non-supported nickel catalysts give rise to polymer characterized by a high level of branching. The melting points of these polymers are anticipated to be as low as to present problems with reactor operation at typical industrial operating temperatures, especially when heat dissipation by solvents is unavailable, as in continuous gas phase polymerization.
Supported diimino nickel or palladium catalysts are disclosed in WO 96/23010, WO 97/48736, WO 98/56832.
WO 96/23010 discloses supported diimino palladium or nickel catalysts. A process wherein a complex activated with a cocatalyst is adsorbed on silica is exemplified.
WO 97/48736 relates to immobilized catalysts; they are substantially obtained by preparing a precursor solution mixing together the complex with an aluminoxane and adding this precursor solution to a porous support.
In some examples of WO 98/56832 the cocatalyst was supported on an inorganic support and then a diimino complex was added, then the obtained catalyst was prepolymerized.
In these applications the diimino ligand is not functionalized for optimizing the bond between the support and the complex. As a result, in the supported catalyst obtained, the migration of the active species into the homogeneous phase during the polymerization reaction may happen.
Therefore the development of a new ligand class that permits a chemical bond between the carTier and the diimino complex is desirable.
An object of the present invention is a new class of diimino ligands functionalized with a siloxy group.
A further object of the present invention is a solid catalyst component for polymerizing olefins comprising: an inorganic support, a diimino ligand chemically bonded to the support and a transition metal.
In this solid component, chemical bonding to the support provides a firm attach of the catalytic centres to the support, resulting in a heterogeneous catalyst component. The preparation of said catalyst precursor results in no contaminating secondary reaction products, hence the catalyst is fiee from undesired impurities. The catalysts can be used in slurry or gas-phase processes. The catalysts are especially useful for the production of branched polyolefins from a single type of monomer.
The present invention relates to diimino compounds defined by following formulae: 
wherein
n is 0 or 1; m is 1, 2 or 3;
each R1, equal to or different from each other, is selected from the group consisting of hydrogen, a monovalent aliphatic or aromatic hydrocarbon group, optionally containing heteroatonis of group 14 to 16 of the periodic table of the elements and boron; with the proviso that al least one R1 group is represented by the formula R5OSi(R)3;
wherein
each R is independently selected from the group consisting of: C1-C20 allkyl, C3-C20 cycloalkyl, C6-C20 aryl, C2-C20 alkenyl, C7-C20 arylalkyl, C7-C20 alkylaryl, C8-C20 arylalkenyl, C8-C20 alkenylaryl liear or branched; preferably it is methyl, ethyl or propyl;
each R5, equal to or different from each other, is a divalent aliphatic or aromatic hydrocarbon group containing from 1 to 20 carbon atoms, optionally containing from 1 to 5 heteroatoms of groups 14, 15 or 16 of the periodic table of the elements and/or boron;
each R2, equal to or different from each other, is a radical which contains from 1 to 20 carbon atoms; this group optionally contains heteroatoms of group 14 to 16 of the periodic table of the elements and/or boron;
R3 is a divalent aliphatic or aromatic hydrocarbon group containing from 1 to 20 carbon atoms, optionally containing from 1 to 5 heteroatoms of groups 14, 15 and 16 of the periodic table of the elements and/or boron;
R4, equal to or different from each other, is hydrogen or a radical which contains from 1 to 20 carbon atoms; this group optionally contains heteroatoms of group 14 to 16 of the periodic table of the elements and/or boron;
This invention also relates to a process to prepare compounds represented by formula I or II above. Likewise this invention relates to a catalyst component comprising the product of the combination of the dilmino ligand and a porous inorganic support.
Further this invention also relates to the use of the catalyst component in combination with a cocatalyst to polymerize olefins
The present invention relates to diimino compounds defined by the following formulae: 
wherein
n is 0 or 1; m is 1, 2 or 3;
each R1, equal to or different from each other, is selected from the group consisting of: hydrogen, a monovalent aliphatic or aromatic hydrocarbon group, optionally containing heteroatoms of group 14 to 16 of the periodic table of the elements and/or boron; with the proviso that al least one R1 group is represented by the formula R5OSi(R)3;
wherein
each R is independently selected from the group consisting of: C1-C20 alkyl, C3-C20 cycloalkyl, C6-C20 aryl, C2-C20 alkenyl, C7-C20 arylalkyl, C7-C20 alkylaryl, C8-C20 arylalkenyl, C8-C20 alkenylaryl linear or branched; preferably it is methyl, ethyl or propyl;
each R5, equal to or different from each other, is a divalent aliphatic or aromatic hydrocarbon group containing from 1 to 20 carbon atoms, optionally containing from 1 to 5 heteroatoms of groups 14, 15 and 16 of the periodic table of the elements and/or boron; preferably it is CR62(R7)aCR62;
wherein
each R6, equal to or different from each other, is selected from the group consisting of: hydrogen or R; two R6 can also unite to form a ring; R7 is selected from the group consisting of: O, NR, S, SiR62, C1-C20 alkylidene, C3-C20 cycloalkylidene, C2-C20 alkenylidene, C6-C20 arylidene, C7-C20 alkylarylidene, C7-C20 arylalkylidene, C8-C20 arylalkenylidene, C8-C20 alkenylarylidene, optionally containing heteroatoms of group 14 to 16 of the periodic table of the elements, and/or boron; a is 0 or 1;
each R2, equal to or different from each other, is a radical which contains from 1 to 20 carbon atoms; this group optionally contains heteroatoms of group 14 to 16 of the periodic table of the elements and/or boron;
preferably R2 is selected from the group consisting of: C1-C20 alkyl, C3-C20 cycloalkyl, C6-C20 aryl, C2-C20 alkenyl, C7-C20 arylalkyl, C7-C20 alkylaryl, C8-C20 arylalkenyl alkenylaryl, linear or branched, optionally substituted by BR62, OR6, SiR63, NR62; most preferably R2 is an alkylsubstituted phenyl, naphthyl, or anthracyl; most preferably R2 is a 2,6 dialkylphenyl group, optionally substituted in position 4 by a group R;
R3 is a divalent aliphatic or aromatic hydrocarbon group containing from 1 to 20 carbon atoms, optionally containing from 1 to 5 heteroatoms of groups 14, 15 and 16 of the periodic table of the elements and/or boron;
Preferably R3 is selected from the group consisting of: (CR62), wherein s is 1 or 2, 
wherein
T is boron, nitrogen or phosphorus; U is boron, oxygen, nitrogen, sulphur or phosphorus;
each R4, equal to or different from each other, is hydrogen or a radical which contains from 1 to 20 carbon atoms; this group optionally contains heteroatoms of group 14 to 16 of the periodic table of the elements and/or boron;
preferably R4 is selected from the group consisting of: hydrogen, C1-C20 alkyl, C3-C20 cycloalkyl, C6-C20 aryl, C2-C20 alkenyl, C7-C20 arylalkyl, C7-C20 alkylaryl, C8-C20 arylalkenyl, C8-C20 alkenylaryl, optionally substituted by BR62, OR6, SiR63 or NR 2;
two or more of R1, R2, R3, R4 and R5 can also unite to form a from 4 to 15 membered aliphatic or aromatic ring; the ring optionally contains heteroatoms of group 14 to 16 of the periodic table of the elements and/or boron.
preferably R1 is selected from the group consisting of: hydrogen, C1-C20 alkyl, C3-C20 cycloalkyl, C6-C20 aryl, C2-C20 alkenyl, C7-C20 arylalkyl, C7-C20 alkylaryl, C8-C20 arylakenyl, C8-C20 alkenylaryl, linear or branched, optionally substituted by BR62, OR6, SiR63, NR62; or R5OSi(R)3;
examples of group CR62(R7)aCR62OSi(R)3 are:
xe2x80x94CH2xe2x80x94CH2xe2x80x94OSiMe3; xe2x80x94CH2xe2x80x94(CH2)pxe2x80x94CH2xe2x80x94OSiMe3 wherein p ranges from 1 to 10;
xe2x80x94CH2xe2x80x94Oxe2x80x94CH2xe2x80x94OSiMe3; xe2x80x94CH2xe2x80x94C6H4xe2x80x94CH2xe2x80x94OSiMe3; xe2x80x94CH(Et)xe2x80x94CH2xe2x80x94OSi(Et)2Me;
xe2x80x94CH2xe2x80x94CH2xe2x80x94Oxe2x80x94CH2OSi(iPr)3; xe2x80x94CH2xe2x80x94Si(CH3)2xe2x80x94CH2xe2x80x94CH2OSi(iPr)3;
xe2x80x94CH2xe2x80x94CH2xe2x80x94Si(CH3)2xe2x80x94CH2OSi(iPr)3; xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94N(CH3)xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2OSi(iPr)3;
xe2x80x94C(Me)2xe2x80x94CH2xe2x80x94C6H4xe2x80x94CH2xe2x80x94CH2xe2x80x94OSi(C5H11)3; xe2x80x94CH2xe2x80x94CH2xe2x80x94C6H4xe2x80x94Oxe2x80x94CH2xe2x80x94CH2xe2x80x94OSi(CH2PH)3;
xe2x80x94C(CH3)2xe2x80x94C(CH3)2xe2x80x94OSi(C6H4Me)3; xe2x80x94CH(Me)xe2x80x94CH(Me)xe2x80x94OSi(Et)(Me)2.
In a particular embodiment the ligand of the present invention can be used for obtaining a solid catalyst component for polymerizing olefins. This solid catalyst component is obtainable by a process comprising the following steps:
a) reacting a diimino ligand of general formula I or II with a porous inorganic support;
b) treating the reaction mixture with a compound of general formula LqMX2, wherein M is selected from the group 8, 9 and 10 of the periodic table, preferably nickel, palladium, iron or cobalt; more preferably nickel; each X, equal to or different from each other, is selected from the group consisting of: halogen, hydrogen, OR, N(R)2, C1-C20 alkyl or C6-C20 aryl; two X taken together can also be an aromatic or aliphatic divalent ligand, containing two equal or different donor atoms belonging to the group 14-16 of the periodic table of the elements, such as catecholate, 1,2-ethanediolate, 1,2-phenylenediamide, xcex1-deprotonated-xcex2-diketone or xcex1-deprotonated-xcex2-ketoester such as acetylacetonate or hexafluoroacetylacetonate; L is a labile ligand; for example L is a neutral Lewis base such as diethylether, tetrahydrofurane, dimethylaniline, aniline, triphenylphosphine, n-butylamine; 1,2 dimethoxyethanie (DME), cyclooctadiene, pyridine, 1,1,2,2-tetramethylendiamine, aromatic or aliphatic nitriles, sulphides, sulphoxides or thiols, triaryl phosphinies, arsines or stibines; and q is 0, 1 or 2.
As porous inorganic support, any type of inorganic oxides can be used, such as: silica, alumina, silica-alumina, aluminium phosphates and mixtures thereof, obtaining supported catalysts with contents in transition metals between 0.01 and 10% by weight, preferably between 0.1 and 4%. Preferably the inorganic support is silica.
The amount of the dilmino ligand which can be anchored in these conditions directly relates to the concentration of the reactive groups present in the support. For this reason a preferred support is silica calcinated at a temperature between 600xc2x0 C. and 800xc2x0 C., preferably in dry atmosphere.
The process for obtaining the solid catalyst component can be carried out in a temperature range from 0 to 200xc2x0 C., in an inert solvent such as non-polar hydrocarbons, for example toluene. Besides, the resulting solid reaction product obtained by this process can be subjected to washing and subsequent filtration.
One advantage of the method here disclosed is that the procedure employed for the formation of the catalyst results in little or no side products that could hamper the polymerisation process. Thus no extra reactants other than the functionalized ligand and the silica are needed. Simple wash of the new modified silica in order to remove unreacted functionalized ligand renders a proper substrate for the second step, the attachment of the metal centre. This step can also be performed in a clean way by ligand interchange at the metal centre. Appropriate choice of the ligand accompanying initially to the metal centre is also desirable in order to facilitate the ligand interchange and to be easily removed by washing and/or evaporation.
The choice of diimino ligand and metal can result in an active catalyst for the polymerisation of olefins. The properties of the polyolefins so obtained can be finely tuned by a selection of the structural properties of the diimino ligand attached to the silica, the nature of the metal centre employed and the polymerisation conditions used (e.g. temperature, pressure, concentration of reactants, etc.).
The co-catalyst is a compound or mixture of compounds that upon reaction with the metal centres render ionic pairs in which the metal centres are alkylated cationic units and the anions are non-coordinating or weakly coordinating. Said co-catalyst is a compound or mixtures of compounds consisting of combinations of alkylating agents and Lewis acids (neutral or cationic) acting simultaneously or in differentiated steps. In cases in which the metal centre is already alkylated, only the Lewis acid, which promotes the formation of a non-coordinating or weakly coordinating anion, is needed. Illustrative but non-limiting examples of co-catalysts are: aluminoxanes (methylaluminoxane (MAO), modified methylaluminoxane (MMAO), isobutylaluminoxane (IBAO), etc.), combinations of alkylaluminiums (such as trimethylaluminium, triethylaluminium, tributylaluminium, etc.) and boron Lewis acids (such as trifluoroborate, trispentafluoroplhenylborane, tris[3,5-bis(trifluoromethyl)phenyl]borane, etc.), hydrogen Lewis acids (dimethylanilinium tetrakis(pentafluorophenyl)boron, HBF4, etc.), silver Lewis acids (such as AgBF4, AgPF6, AgSbF6, silver tetrakis[3,5-bis(trifluoromethyl)phenyl]borate etc.) or others (such as sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, etc.).
Compounds of fonnula I and II, wherein at least one R5 is represented by the formula CR62(R7)aCR62OSi(R)3, are preferably prepared by a process comprising the following steps:
1) reacting a compound represented by formula III or IV 
xe2x80x83wherein each Z is independently selected from the group consisting of: R1 and CR62H, provided that at least one Z is represented by the formula CR62H, with a Bronsted base preferably selected from the group consisting of: organolithium compounds, orgaiiosodium compounds, organopotassium compounds, organomagnesiums, sodium hydride, potassium hydride, lithium, sodium, or potassium; preferably lithium alkyl, sodium alkyl, potassium alkyl; more preferably butyllithium; and
2) contacting the obtained metallated compound with one equivalent of a compound of general formula Y(R7)aCR62OSi(R)3 wherein Y is a leaving group, preferably halogen, sulfonate groups, more preferably iodine or bromine.
While not wishing to be bound by theory, it is believed that, in the above procedure, advantage has been taken of acidity of hydrogen atoms bonded to a carbon in the alpha position to the imino group. Thus, it is believed that following a selection of the base to be used, one acidic proton at the carbon atom at the alpha position of the imino group is removed, resulting in an anionic species which is believed to be prone to act as a nucleophile in the presence of an electrophile. Thus a new bond can be formed when these two species interact. It is commonly known that such a new bond can be formed through two general pathways: by substitution or by addition. In the first case a leaving group is detached fromlthe electrophilic centre. In the second case, a bond is broken (for instance a double bond becomes a single bond).
In order to have the alkoxysilane functional group in the final ligand thus formed, this functional group, or a suitable precursor of it, is preferably already present in the electroplhile.
According to this synthetic procedure, choosing a base is desirable in order to selectively remove a hydrogen atom from the carbon atom in alpha to the imino group and, at the same time, not promoting undesired secondary reactions (for instance addition to the imine double bond). Also a suitable leaving group Y is preferably present in the electrophile in order to facilitate the formation of the new bond.
The synthetic method of the present invention has also the advantage of providing the possibility of linking more than just one functional group as long as there are more hydrogen atoms at the carbon atom in an alpha position to any of the two imino groups in the diimino precursor. It is sufficient to adjust the amount of base to be added to the original diimine in order to remove the desired number of hydrogen atoms. The process is preferably carried out under inert atmosphere for example nitrogen or argon and with dried solvents.
Non limitative examples of compounds represented by formula Y(R7)aCR62OSi(R)3 are: Clxe2x80x94CH2xe2x80x94OSiMe3, Clxe2x80x94CH2xe2x80x94CH2xe2x80x94OSiMe3, Clxe2x80x94(CH2)2xe2x80x94CH2xe2x80x94OSiMe3, Clxe2x80x94(CH2)3xe2x80x94CH2xe2x80x94OSiMe3, Clxe2x80x94(CH2)4xe2x80x94CH2xe2x80x94OSiMe3, Clxe2x80x94(CH2)5xe2x80x94CH2xe2x80x94OSiMe3, Clxe2x80x94(CH2)6xe2x80x94Cl2xe2x80x94OSiMe3, Clxe2x80x94(CH2)7xe2x80x94CH2xe2x80x94OSiMe3, Clxe2x80x94CH2xe2x80x94C6H4xe2x80x94CH2xe2x80x94OSiMe3, Clxe2x80x94(CH2)8xe2x80x94CH2xe2x80x94OSiMe3, Clxe2x80x94(CH2)9xe2x80x94CH2xe2x80x94OSiMe3, Clxe2x80x94(CH2)10xe2x80x94CH2xe2x80x94OSiMe3, Clxe2x80x94CH2xe2x80x94CMe2xe2x80x94CH2xe2x80x94OSiMe3, Clxe2x80x94CH2xe2x80x94CMe2xe2x80x94CH2xe2x80x94OSiMe3, Clxe2x80x94CH2xe2x80x94CMe2xe2x80x94CMe2xe2x80x94CH2xe2x80x94OSiMe3, Clxe2x80x94CH2xe2x80x94C6H4xe2x80x94Oxe2x80x94CH2xe2x80x94OSiMe3, Clxe2x80x94CMe2xe2x80x94CH2xe2x80x94OSiMe3, Clxe2x80x94CH2xe2x80x94CEtMexe2x80x94CH2xe2x80x94OSiMe3, Clxe2x80x94CH2xe2x80x94CEt2xe2x80x94CH2xe2x80x94CH2xe2x80x94OSiMe3, Clxe2x80x94CH2xe2x80x94CMe2xe2x80x94CEt2xe2x80x94CH2xe2x80x94OSiMe3, Clxe2x80x94CH2xe2x80x94C6H4xe2x80x94Oxe2x80x94CH2xe2x80x94OSiMe3, Clxe2x80x94CEt2xe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94CH2xe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94(CH2)2xe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94(CH2)3xe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94(CH2)4xe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94(CH2)5xe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94(CH2)6xe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94(CH2)7xe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94CH2xe2x80x94C6H4xe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94(CH2)8xe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94(CH2)9xe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94(CH2)10xe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94CH2xe2x80x94CMe2xe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94CH2xe2x80x94CMe2xe2x80x94CH2xe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94CH2xe2x80x94CMe2xe2x80x94CMe2xe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94CH2xe2x80x94C6H4xe2x80x94Oxe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94CMe2xe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94CH2xe2x80x94CEtMexe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94CH2xe2x80x94CEt2xe2x80x94CH2xe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94CH2xe2x80x94CMe2xe2x80x94CEt2xe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94CH2xe2x80x94C6H4xe2x80x94Oxe2x80x94CH2xe2x80x94OSiMe3, Brxe2x80x94CEt2xe2x80x94CH2xe2x80x94OSMie3, Ixe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94CH2xe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94(CH2)2xe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94(CH2)3xe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94(CH2)4xe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94(CH2)5xe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94(CH2)6xe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94(CH2)7xe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94CH2xe2x80x94C6H4xe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94(CH2)8xe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94(CH2)9xe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94(CH2)10xe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94CH2xe2x80x94CMe2xe2x80x94CH2OSiMe3, Ixe2x80x94CH2xe2x80x94CMe2xe2x80x94CH2xe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94CH2xe2x80x94CMe2xe2x80x94CMe2xe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94CH2xe2x80x94C6H4xe2x80x94Oxe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94CMe2xe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94CH2xe2x80x94CEtMexe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94CH2xe2x80x94CEt2xe2x80x94CH2xe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94CH2xe2x80x94CMe2xe2x80x94CEt2xe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94CH2xe2x80x94C6H4xe2x80x94Oxe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94CEt2xe2x80x94CH2xe2x80x94OSiMe3, Ixe2x80x94CH2xe2x80x94OSiEt3, Ixe2x80x94CH2xe2x80x94CH2xe2x80x94OSiEt3, Ixe2x80x94(CH2)2xe2x80x94CH2xe2x80x94OSiEt3, Ixe2x80x94(CH2)3xe2x80x94CH2xe2x80x94OSiEt3, Ixe2x80x94(CH2)4xe2x80x94CH2xe2x80x94OSiEt3, Ixe2x80x94(CH2)5xe2x80x94CH2xe2x80x94OSiEt3, Ixe2x80x94(CH2)6xe2x80x94CH2xe2x80x94OSiEt3, Brxe2x80x94(CH2)7xe2x80x94CH2xe2x80x94OSiPr3, Brxe2x80x94CH2xe2x80x94C6H4xe2x80x94CH2xe2x80x94OSiPr3, Brxe2x80x94(CH2)8xe2x80x94CH2xe2x80x94OSiPr3, Brxe2x80x94(CH2)9xe2x80x94CH2xe2x80x94OSiPr3, Brxe2x80x94(CH2)10xe2x80x94CH2xe2x80x94OSiPr3, Brxe2x80x94CH2xe2x80x94CMe2xe2x80x94CH2xe2x80x94OSiPr3, Clxe2x80x94CH2xe2x80x94CMe2xe2x80x94CH2xe2x80x94CH2xe2x80x94OSiPh3, Clxe2x80x94CH2xe2x80x94CMe2xe2x80x94CMe2xe2x80x94CH2xe2x80x94OSiPh3, Clxe2x80x94CH2xe2x80x94C6H4xe2x80x94Oxe2x80x94CH2xe2x80x94OSiPh3, Clxe2x80x94CMe2xe2x80x94CH2xe2x80x94OSiPh3, Clxe2x80x94CH2xe2x80x94CEtMexe2x80x94CH2xe2x80x94OSiPh3, Clxe2x80x94CH2xe2x80x94CEt2xe2x80x94CH2xe2x80x94CH2xe2x80x94OSiPh3, Brxe2x80x94CH2xe2x80x94CMe2xe2x80x94CEt2xe2x80x94CH2xe2x80x94OSiMeEt2, Brxe2x80x94CH2xe2x80x94C6H4xe2x80x94Oxe2x80x94CH2xe2x80x94OSiPhMe2, Brxe2x80x94CEt2xe2x80x94CH2xe2x80x94OSiEtPr2.
More preferred diimino compounds represented by formula I are: 
Non limiting examples of compounds according to formula I are: 
The nickel or palladium catalyst of the present invention is especially useful for the production of branched polyethylene without requiring a co-monomer.
As those of skill in the art will appreciate it, the polymerization procedure can change according to the chosen type of polymerization process (solution, suspension, slurry or gas phase).
The process comprise contacting the monomer, or, in certain cases, the monomer and the comonomer, with a catalytic composition according to the present invention.
The alpha-olefins that can be used as comonomers to obtain ethylene copolymers can be one or more C3-C12 linear or branched alpha olefin, such as propylene, butene, hexene, octene or branched ones such as the 4-methyl-1-pentene and can be used in proportions from 0.1 to 70% by weight of the total of the monomers. In the case of ethylene polymerization the density of polymers can be as low as 0.86 g/cm3.
In the particular case of the polymerization technique known as suspension process or controlled particle morphology process and in case of gas-phase process, the used temperature is preferably between 30xc2x0 and 100xc2x0 C., while for the solution process the usual temperature will be between 120xc2x0 and 250xc2x0 C.
The pressure will change according to the polymerization technique; it will range from atmospheric pressure to 350 MPa.